Greetings, magellanic!
While statistics that exactly match your specifications do not exist,
I believe that I can provide you with information that will give you a
good Answer. Bear in mind that such figures are -- by necessity --
estimates, and may vary among different sources.
Another account of the recent spectacular meteorite event that hit the
Midwest can be found on Space.com - "Meteor Showers Rocks on
Midwestern Homes" by Rick Callahan, Associated Press (March 28, 2003):
"Paul Sipiera, a professor of geology and astronomy at Harper College
in Palatine, Ill., spent Thursday examining dozens of pieces of
meteorites and plotting where they fell. The largest he saw was about
7 1/2 pounds.
He said the debris field appears to cover a path about 80 miles long
by 20 miles wide from north of Bloomington, Ill., to Chicago's south
side and possibly part of northwestern Indiana.
He said all of the pieces came from a stony meteorite he estimates was
about the size of a Volkswagen bug when it exploded as it plunged into
Earth's atmosphere...
Sipiera said it's very rare for meteorites to fall on populated
areas."
http://www.space.com/scienceastronomy/solarsystem/midwest_meteors_030228.html
According to the CNN.com Space article "Rock hunters bag five Mars
meteorites" (January 25, 2002) [this article does not specify size],
it says:
"An estimated 20,000 meteorites strike the Earth every year..."
http://www.cnn.com/2002/TECH/space/01/24/mars.rocks/
From the British National Space Centre's page on Meteors:
"About 10,000 football-sized meteorites hit the Earth each year..."
http://www.bnsc.gov.uk/index.cfm?pid=646
From Prof. Stephen A. Nelson's Geology 204 "Meteorites, Impacts, and
Mass Extinction" lecture at Tulane University (July 29, 2002):
"Throughout history there have been reports of stones falling from the
sky, but the scientific community did not recognize the
extraterrestrial origin of meteorites until the 1700s. Within recent
history meteorites have even hit humans-
1938 - a small meteorite crashed through the roof of a garage in
Illinois
1954 - A 5kg meteorite fell through the roof of a house in Alabama.
1992 - A small meteorite demolished a car near New York City."
Professor Nelson goes on to say:
"Tons of micrometeorites strike the Earth each day. Because of their
small size, they do not usually burn up when entering the Earth's
atmosphere, but instead settle slowly to the surface. Meteorites with
diameters of about 1 mm strike the Earth about once every 30 seconds.
Upon entering the Earth's atmosphere the friction of passage through
the atmosphere generates enough heat to melt or vaporize the objects,
resulting in so called shooting stars. Meteorites of larger sizes
strike the Earth less frequently. If they have a size greater than
about 2 or 3 cm, they only partially melt or vaporize on passage
through the atmosphere, and thus strike the surface of the Earth...
a 1 km sized object strikes the Earth about once every million years,
and 10 km sized objects about once every 100 million years."
http://www.tulane.edu/~sanelson/geol204/impacts.htm
There is a great picture of the 1954 Alabama meteorite -- the only one
known to have actually hit a human -- on NASA's StarChild site:
"There has only been one report of a "HBM" (hit by meteorite), and
that occurred in 1954. Ann Hodges of Sylacauga, Alabama was slightly
injured when a 19.84 kilogram meteorite crashed through the roof of
her home."
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/meteoroids.html
From Cornell University's Astronomy Department's "Curious About
Astronomy" by Lynn Carter (February 2003):
"Q: How many meteorites hit the earth each year, and how do they
determine that?
A: ...I can still find a lot of different estimates for how much
stuff hits Earth each year, partly because different studies look at
different size ranges, and all the procedures have errors. Estimates
for the mass of material that falls on Earth each year range from
37,000-78,000 tons. Most of this mass would come from dust-sized
particles...
A study done in 1996 (looking at the number of meteorites found in
deserts over time) calculated that for objects in the 10 gram to 1
kilogram size range, 2900-7300 kilograms per year hit Earth. However,
unlike the number above this does not include the small dust
particles. They also estimate between 36 and 166 meteorites larger
than 10 grams fall to Earth per million square kilometers per year.
Over the whole surface area of Earth, that translates to 18,000 to
84,000 meteorites bigger than 10 grams per year... (This study was led
by P. A. Bland and was published in Monthly Notices of the Royal
Astronomical Society.)"
http://curious.astro.cornell.edu/question.php?number=470
You can find some excellent information about large Meteorites on the
Natural History Museum of Los Angeles County's website:
http://www.nhm.org/research/minsci/exmeteor.htm
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Regards,
aceresearcher |
